COCI 2007/2008, Contest #1

Task CETVRTA

Mirko needs to choose four points in the plane so that they form a rectangle with sides parallel to the
axes. He has already chosen three points and is confident that he hasn't made a mistake, but is having
trouble locating the last point. Help him.

Input

Each of the three points already chosen will be given on a separate line. All coordinates will be integers
between 1 and 1000.